Fatty acids are essential nutrients of human cells but are also central players, if not causative agents, in several common diseases, including myocardial ischemia, diabetes and obesity. Acutely elevated leels of FA following an ischemic event disturb membrane-related functions such as contraction, excitability, rhythm and cell viability. Chronically elevated acids may be a direct causative agent in type II diabetes. Less common genetic disorders of fatty acid oxidation such as adrenoleukodystrophy (ALD) are characterized by accumulation of specific fatty acids, very long chain saturated fatty acids (VLCFA). This project uses state-of-the- art methods in both structural and cell biology to describe structural and dynamic aspects of fatty acid binding interactions and transport in plasma, cell membranes, and serum albumin by differential scanning calorimetry and 13C NMR and fluorescence spectroscopy, and studies the metabolic fate of VLCFA in cells of ALD patients by novel 13C NMR approaches. The second aim determines the complete tertiary structure in solution of intracellular fatty acid and lipid binding proteins (FABP); these structures provide a basis for elucidating molecular details of protein dynamics and ligand binding. Binding of less abundant ligands such as immediate products of fatty acid metabolism will be studied to elucidate new potential functions of FABP. The third aim studies the transport of fatty acids in membranes and tests both major hypotheses of fatty acid transport through the lipid bilayer, passive diffusion and protein-mediated transporter. This aim will use a combination of fluorescence probes to quantitative the adsorption and transmembrane movement steps of fatty acid transport in cells. Our studies of the fundamental and complex physical interactions and properties of fatty acids will prove indispensable knowledge for interpreting the behavior of fatty acids in physiological systems and delineating their precise roles in human diseases.